1. Field of Use
The invention is associated with the oil and gas industry, in particular with the methods of near-wellbore treatment of a reservoir to enhance fluid production. The proposed reservoir treatment creates secondary multidirectional fractures in treated intervals. This increases the permeability of the near-wellbore zone of the reservoir and its productivity in the extraction of oil, gas, gas-condensate, injection thermal and other mineral waters.
2. Background Technology
Various means of treating the near-wellbore zone of the reservoir using the technology of thermo-acidic treatment of the near-wellbore zone of the reservoir are known.
For example, existing technology is using thermal energy created through the interaction of solutions of HCl and metal magnesium (Mishchenko. I. T. Well production. Oil and Gas. 2007, UDC 622.276.5 p. 253-256). This technology reaction between magnesium and hydrochloric acid occurs in a well bore with the release of thermal energy. Temperature increase of the hydrochloric acid and the reservoir promote melting of the paraffin and resin deposits and their removal from the near well bore zone.
After dissolving paraffin-resin deposits through an increase in effective temperature, the residual, partially spent acid solution, that is left from the reaction with magnesium, continues to dissolve soluble formation material. This will effectively increase the size of existing channels. However, this method has a number of significant disadvantages:                (1) Low temperature and the washing abilities of acid, which are insufficient to create channels and fractures in the reservoir;        (2) The acid concentration in solution decreases after the reaction with magnesium;        (3) Reduction of acid concentration lowers its effectiveness in dissolving near wellbore formation;        (4) The acidic solution has relatively low washing abilities necessary to change the wettability and to remove the paraffin-resinous rock deposits; and        (5) Acid impacts only channels and fractures existent at the time of treatment.        
The closest in the technical sense to the claimed technology is the method of thermochemical treatment of the near well bore formation zone by pumping a suspension of granulated magnesium and ammonium nitrate in an oil-based fluid into this zone, with the subsequent injection of hydrochloric acid solution into the reservoir such as taught in USSR Patent No. SU640023 to Abdulin et al., 1978-12-30. As described in SU640023, the hydrochloric acid reacts with magnesium, thus increasing the temperature of the acid and initiating the decomposition of ammonium nitrate. The main sources of heat in the this technology are: the reaction of magnesium with hydrochloric acid, the decomposition of ammonium nitrate and the final stage of processing where combustion of hydrogen and nitric oxide is possible. The disadvantages of the method in SU640023 are:                (1) The acidic component reacts with magnesium, thus lowering the concentration of hydrochloric acid, and hence the activity in interaction with the formation;        (2) High temperature is required for the decomposition of ammonium nitrate. Therefore, increasing the temperature will require a large consumption of acid and there is a high probability of failure to heat ammonium nitrate until decomposition; and        (3) The final stage of the process involves the explosion of a gas mixture of hydrogen and oxygen, which could adversely affect the condition of the cement isolation and casing of the treated intervals.        
Therefore, it is a technical objective of the present invention to provide a method that will improve the effect of the near-wellbore zone treatment, while ensuring the safety of the process.